Process and plant for building tyres for vehicle wheels

ABSTRACT

A process for building tyres for vehicle wheels includes the steps of: i) building a carcass structure of a green tyre in at least one carcass structure building line, the carcass structure including at least one carcass ply and a pair of annular anchoring structures; ii) building a crown structure of a green tyre in at least one crown structure building line, the crown structure including a belt structure and a tread band; wherein step ii) of building the crown structure includes at least one step iii) of building the belt structure which in turn includes the steps of: a) building on at least one first building drum, an annular assembly including a first radially inner belt layer and at least a second belt layer radially external to the first belt layer; b) transferring the annular assembly on at least one auxiliary drum; c) turning up axially opposite end portions of the fast radially inner belt layer so as to obtain at least a partial overlapping of the end portions of the first belt layer on the at least one second radially outer belt layer; and d) transferring said annular assembly from the at least one auxiliary drum on at least one second building drum.

The present invention relates to a process for building tyres forvehicle wheels.

The present invention also relates to a plant for building tyres forvehicle wheels, usable for carrying out the above mentioned buildingprocess.

Tyre production cycles comprise a building process, wherein the variouscomponents of the tyre itself are made and/or assembled in one or morebuilding lines, and subsequently a moulding and vulcanization process iscarried out in a suitable vulcanization line, adapted for defining thetyre structure according to a desired geometry and tread pattern.

A tyre generally comprises a toroidally ring-shaped carcass includingone or more carcass plies, strengthened with reinforcing cords lying insubstantially radial planes (a radial plane contains the rotation axisof the tyre). Each carcass ply has its ends integrally associated withat least one metal reinforcing annular structure, known as bead core,constituting the reinforcing at the beads, i.e. at the radially innerends of the tyre, having the function of enabling the assembling of thetyre with a corresponding mounting rim. Placed crown wise to saidcarcass is a band of elastomeric material, called tread band, withinwhich, at the end of the moulding and vulcanization steps, a raisedpattern is formed for ground contact. A reinforcing structure, generallyknown as belt structure, is arranged between the carcass and the treadband. Such structure usually comprises, in the case of car tyres, atleast two radially superposed layers of rubberised fabric provided withreinforcing cords, usually of metal material, arranged parallel to eachother in each layer and in a crossed relationship with the cords of theadjacent layer, preferably symmetrically arranged with respect to theequatorial plane of the tyre. Preferably, the belt structure furthercomprises at a radially outer position thereof, at least on the ends ofthe underlying belt layers, also a third layer of textile or metalliccords, circumferentially disposed (at zero degrees).

The belt structure and the tread band together form the so called “crownstructure” of the tyre.

Finally, in tyres of the tubeless type, a radially inner layer, calledliner, is present which has imperviousness features for ensuring theair-tightness of the tyre itself.

To the aims of the present invention and in the following claims, by theterm “elastomeric material” it is intended a composition comprising atleast one elastomeric polymer and at least one reinforcing filler.Preferably, such composition further comprises additives such ascross-linking and/or plasticizing agents. By virtue of the cross-linkingagents, such material may be cross-linked by heating, so as to form thefinal manufactured article.

In the present context, by the term “green tyre” it is indicated a tyreobtained by the building process and not moulded and vulcanized yet.

WO 01/32409, in the name of the same Applicant, describes a tyrebuilding line provided with working stations, each arranged to make andassemble at least one structural component of the tyre being processed,wherein at least one series of tyres is treated at the same time,comprising at least one first and a second model of tyres differing fromeach other, and wherein the tyre transfer to the vulcanization line iscarried out through robotized arms and according to a transferring rateequal to the transferring rate of the tyres to each of said workingstations.

EP 1 481 791 A2 describes a method of simultaneously producing tyres ina multi-phase sequential production system, the tyres being selectedfrom a group of tyres with different build specifications in differentsizes. The method comprises the steps of selecting the tyre buildingequipment and materials required for constructing the respective type oftyre; calculating the corresponding number of cycles that each buildingequipment must perform to build a given lot; and automatically changingto a second building specification at a lot change, by switching to thesecond building specification after the last tyre of the first buildingspecification passes; repeating the automatic changing to the nextbuilding specification at each station as each last tyre of each priorlot passes until a final lot is produced. The production system has atleast four carcass building stations, each station being spaced at apredetermined distance, and preferably a crown structure building line,having working stations, separate from the carcass building line,wherein the carcass and the crown structures are joined in a segmentedself-locking mould.

EP 0 015 113 A1 describes a machine and a method for folding thecircumferential edge portions of a tyre component. The folding machinecomprises: an annular deck having a cylindrical support surface for thecomponent and a precisely formed sharply shouldered peripheral deckedge, and a bladder assembly positioned axially and radially inwardly ofsaid deck edge cooperating when inflated with said deck edge to fold theoverhanging circumferential edge portion of the component at such deckedge.

The methods of the type described in WO 01/32409 are aimed at increasingproductivity in manufacturing processes of tyres built on a toroidalforming support and using elementary semi-finished products for buildingby automated, standardised steps, synchronised with each other. Suchmethods, however, do not allow obtaining a high technologicalflexibility, that is, the possibility of using for each tyre elementarysemi-finished products differing by type of elastomeric material or bytype of textile or metal reinforcing cord. In fact, such methods aresuitable for producing tyres that differ in limited features, such asdimensions, optional presence of some structural components of thetyre—such as one or two carcass plies, reinforcing elements in beadzone—, arrangement of the coils of rubber metal wires forming the beadcores in the bead zone, more or less extended belt layer at zerodegrees, presence of a layer and sublayer in the tread band.

The method illustrated in EP 1 481 791, on the other hand, istechnologically flexible as it allows obtaining tyres with semi-finishedproducts having different features from one another, but it is limitedin terms of productivity, for example as the model of tyre to beproduced changes and require large sized plants for carrying out them.

The Applicant has also noted that in the production plants of thislatter type, the management of a large number of materials and/orsemi-finished products causes problems in synchronising the productionsteps of the various portions making up the tyre and thereby problems inthe general management of the production plant with negativeconsequences on productivity.

The folding methods of the type described in EP 0 015 113 have thepurpose of obtaining precise and well defined folding of tyrecomponents, but they do not pursue nor attain high productionflexibility and productivity.

In order to obtain a process and a plant for producing tyres wherein itis possible to make even high and very high performance tyres, with ahigh production ability and high technological flexibility, wherein itis necessary to carry out folding operations in some components of thetyre, the Applicant has found that by inserting machines of the typeillustrated in EP 0 015 113 A1 in the production methods of the typeillustrated in WO 01/32409 and EP 1 481 791, the illustrated problemsrelating to the flexibility or productivity of the above methodsremained unchanged or became more critical.

The Applicant has therefore perceived that in order to produce tyresthat require folding operations of at least one component in thebuilding step, with technological requirements very different from oneanother, improving the productivity of processes of the type shown in WO01/32409, and avoiding production plants of large dimensions anddifficult to manage and synchronise like those illustrated in EP 1 481791 A2, it is necessary to have a production plant provided with atleast one work station dedicated to the above operation, in line withthe concerned part of plant.

The Applicant has further noted that if the above folding operation mustbe carried out between the layers making up the tyre belt structureduring the building of the same, such dedicated work station must berapid both in the folding operations and in the inlet/outlet of thecomponents to be folded, and very flexible from the point of view of thedimensions and materials used in the tyre to be produced.

The Applicant has thus perceived that having a tyre building plantprovided with a crown structure building line comprising at least onefirst building drum of an annular assembly made by a plurality of beltlayers, and a turning up work station comprising at least one auxiliarydrum and at least one device for transferring the annular assembly fromthe building drum to the auxiliary drum and from the latter to at leastone second building drum it is possible to simultaneously produce smallbatches of tyres with a high technological complexity anddifferentiation achieving high productivity and quality of the finalproduct.

Finally, the Applicant has found that carrying out a tyre buildingprocess comprising a step of building the belt structure which in turncomprises the steps of building on at least one first building drum anannular assembly comprising a plurality of belt layers, transferring theannular assembly on at least one auxiliary drum, turning up the ends ofthe belt layers, and transferring the annular assembly with the endsturned up on at least one second building drum, it is possible to obtainhigh technological flexibility tyres while keeping also the productivityhigh.

More precisely, in accordance with a first aspect thereof, the inventionrelates to a process for building tyres for vehicle wheels comprisingthe steps of:

i) building a carcass structure of a green tyre in at least one carcassstructure building line, said carcass structure comprising at least onecarcass ply and a pair of annular anchoring structures;ii) building a crown structure of a green tyre in at least one crownstructure building line, said crown structure comprising a beltstructure and a tread band;wherein the step ii) of building the crown structure comprises at leastone step iii) of building the belt structure which in turn comprises thesteps of:a) building on at least one first building drum an annular assemblycomprising a first radially inner belt layer and at least one secondbelt layer radially external to said first belt layer;b) transferring said annular assembly on at least one auxiliary drum;c) turning up axially opposite end portions of the first radially innerbelt layer so as to obtain at least a partial overlapping of the endportions of the first belt layer on said at least one second radiallyouter belt layer;d) transferring said annular assembly from said at least one auxiliarydrum on at least one second building drum.

Being compatible with the possibility of using elementary semi-finishedproducts differing for each tyre produced, providing the transfer of theannular assembly from a building drum to an auxiliary drum, theperformance of the belt turning up step on such auxiliary drum and thesubsequent transfer of the annular assembly on a second building drum,said process allows obviating the aforementioned disadvantages of lowtechnological flexibility, keeping high performance quality of thefinished product and high productivity even for tyres that requirecomplex assembly operations wherein there is at least one folding actionon the components subject to building operations.

The process according to the present invention therefore istechnologically flexible and efficient.

Finally, since the building process according to the present inventionprovides the transfer of the annular assembly from the auxiliary drum ona second building drum, it attains the advantage of allowing time bytime the selection of the most suitable type of drum for the operationsto be carried out.

In accordance with a second aspect thereof, the invention relates to aplant for building tyres for vehicle wheels comprising:

-   -   at least one carcass structure building line, said carcass        structure comprising at least one carcass ply and a pair of        annular anchoring structures;    -   at least one crown structure building line, said crown structure        comprising at least one belt structure and a tread band;        wherein the crown structure building line comprises:    -   at least one first building drum whereon an annular assembly        comprising a first radially inner belt layer and at least one        second belt layer radially external to said first belt layer is        built;    -   at least one auxiliary drum whereon axially opposite end        portions of said first belt layer are turned up on said at least        one second belt layer;    -   at least one second building drum suitable for receiving the        annular assembly with the axially opposite end portions of said        first belt layer turned up on said at least one second belt        layer; and    -   at least one device for transferring said annular assembly from        said at least one first building drum to said at least one        auxiliary drum and from said at least one auxiliary drum to said        at least one second building drum.

Carrying out the above process, said plant achieves the same advantagesmentioned above.

The Applicant has further noted that the building plant, providing anauxiliary drum whereon the turning up operation is carried out which isseparate from the building drum, and a transfer device to and from saidauxiliary drum, allows overcoming also the above disadvantages oftechnological flexibility, since it is possible to select time by timethe most suitable features of the drums for the type and performance ofthe tyre to be produced.

The present invention, in at least one of the above aspects thereof, canexhibit at least one of the following preferred features.

In one embodiment of the present invention, said process provides thatthe above step a) of building the annular assembly comprises the furtherstep of building a third belt layer.

Preferably, said belt layer is radially external to said second beltlayer.

In this case, the step c) of turning up comprises the step of turning upaxially opposite end portions of said first radially inner belt layer soas to obtain at least a partial overlapping of the end portions of thefirst belt layer on said second layer and on said third belt layerradially external to said second belt layer.

Preferably, said third belt layer is radially internal to said firstbelt layer.

According to one embodiment of the invention, the second building drumis equal to the first building drum. This is economically advantageouswhen the product requirements allow the use of a single building drum,or when it is possible to optimise both the pre-turning up and thepost-turning up operations with a single building drum.

The step iii) of building the belt structure advantageously comprises,before the step a) of building the annular assembly, the step of:

a1) applying an under-belt layer in a position radially external to thefirst building drum.

Such under-belt layer has the function of releasing the end of the beltstructure from the carcass structure for reducing the stresses generatedin operation.

Preferably, the step a) of building the annular assembly comprises thesub-step of:

a2) laying at least one intermediate element on the first belt layer.After step d), step iii) comprises a step e) of:applying at least one first layer of textile or metal cords, arrangedcircumferentially, in a position radially external to said annularassembly.

The step ii) of building the belt structure comprises, after the step e)of applying at least one cord layer, a step f) of:

applying at least one tread band in a position radially external to saidcord layer.

The step ii) of building the belt structure comprises, after the step f)of applying the tread band, a step g) of:

applying at least a portion of sidewalls of the tyre being processed ina position axially external to said tread band.

Advantageously, the step c) of turning up is carried out in a turning upwork station of the crown structure building line.

Preferably, the step b) of transferring the annular assembly on theauxiliary drum is carried out in a turning up work station of the crownstructure building line.

Preferably, the step d) of transferring the annular assembly on thesecond building drum is carried out in a turning up work station of thecrown structure building line.

Preferably, the step ii) of building the belt structure comprises,before step f) of applying the tread band, the sub-step f′) of applyingat least one tread band sublayer on the cord layer applied in step e).

According to one embodiment of the invention, step f) comprises theapplication of two layers of tread band.

Preferably, at least one between step f) and sub-step f′) is carried outby applying at least one continuous elongated element of elastomericmaterial according to side by side or partially overlapped coils in aposition radially external to said belt structure.

Advantageously, at least one between step a1) and step a2) is carriedout by applying at least one continuous elongated element of elastomericmaterial according to side by side or partially overlapped coils in aposition radially external respectively to said first building drum orto said first belt layer.

According to preferred embodiments, at least one between steps a) and e)comprises the pre-step h) of supplying elementary semi-finished productsin the respective work stations.

Preferably, said elementary semi-finished products are strips ofelastomeric material cut to size and comprising at least one textile ormetal elongated reinforcing element thereinside.

Preferably, said elementary semi-finished products are applied next toone another so that the longitudinal axis thereof exhibits at leastalong a portion the same predetermined angle with the circumferentialdirection of the first building drum.

The process according to the invention may comprises the additional steph′) of preparing elementary semi-finished products in a semi-finishedproduct preparation line.

According to preferred embodiments, the process further comprises thestep j) of adjusting the dimensions of at least one between the firstbuilding drum, the second building drum and the auxiliary drum.

Advantageously, said step j) comprises the radial adjustment of thefirst building drum.

Advantageously, said step j) comprises the radial adjustment of thesecond building drum.

Advantageously, said step j) comprises the radial and axial adjustmentof the auxiliary drum.

This ensures high product and technological flexibility.

Preferably, at least one between the first and the second building drumis transferred from a work station of the crown structure building lineto the next work station by at least one robotized arm.

According to one preferred embodiment, step b) of transferring saidannular assembly on at least one auxiliary drum is carried out bytransfer devices.

Preferably, said transfer devices also perform the step d) oftransferring said annular assembly from said at least one auxiliary drumon said at least one first or second building drum.

The tyre building process according to one embodiment of the invention,further comprises at least a step k) of adjusting the dimensions of saidtransfer devices.

Preferably, such adjustment takes place in radial direction so that thetransfer devices are suitable for finished products of differentdimensions.

Preferably, such adjustment takes place in axial direction so that thetransfer devices are suitable for products with different technologicalrequirements.

Advantageously, at least one between step b) of transferring the annularassembly on at least one auxiliary drum and step d) of transferring theannular assembly on the first or second building drum is followed by astep l) of shaping the belt structure.

Preferably, said step l) is carried out by expanding the auxiliary drum.

Even more preferably, said step l) is carried out by expanding at leastone between said first building drum and second building drum.

The plant for building tyres for vehicle wheels, according to onealternative embodiment, provides that the second building drum coincideswith the first building drum, so as to achieve the above advantages.

According to preferred embodiments, the second building drum isgeometrically different from the first building drum.

Such feature allows choosing the most geometrically suitable drum forthe steps to be performed.

For example, if the technological requirements of a product require theaxial laying (that is, at 90 degrees) in a position radially external tosaid first building drum of reinforcing elements of elastomeric materialcomprising at least one textile or metal elongated reinforcing element,it is necessary to have a drum whose outer surface is flat, that is,does not exhibit concavity or convexity.

In fact, only in this way it is possible to have contiguous elementswithout discontinuity or overlapping.

However, the subsequent laying of textile or metal cords, arrangedcircumferentially (at 0 degrees), in radially outer position, at leaston the ends of the underlying belt layers, must necessarily be carriedout on an already shaped tyre, and thus supported by a drum providedwith a convex outer surface, since such layer cannot be subject totraction due to the poor elastic properties thereof.

The possibility of having building drums differing from the geometricalpoint of view therefore ensures the optimal execution of each step ofthe process according to the invention.

In particular, it is preferable that the second building drum comprisesa shaping surface.

Preferably, the auxiliary drum is geometrically different from the firstbuilding drum.

Preferably, the auxiliary drum comprises a shaping surface.

Even more preferably, said shaping surface is convex.

According to one embodiment of the invention, the crown structurebuilding line comprises at least one turning up work station comprisingthe auxiliary drum and the transfer device.

Preferably, the turning up work station further comprises devices forturning up at least one part of the axially opposite end portions of thefirst belt layer on said at least one second belt layer, suitable forcooperating with the auxiliary drum.

According to one embodiment of the invention, the crown structurebuilding line also comprises a work station for applying the under-beltlayer provided with devices for applying an under-belt layer on thefirst building drum.

Said devices preferably comprise a dispenser of a continuous elongatedelement of elastomeric material and actuators for moving the firstbuilding drum so as to wind said continuous elongated element accordingto side by side or at least partially overlapped coils in a positionradially external to the first building drum.

The crown structure building line advantageously comprises, upstream ofthe turning up work station, the following work stations:

-   -   a work station for applying a first belt provided with devices        for applying at least one first belt layer in a position        radially external to the first building drum;    -   a work station for applying a second belt provided with devices        for applying a second belt layer in a position radially external        to the first belt layer.

Preferably, the crown structure building line comprises, downstream ofthe turning up work station, the following work stations:

-   -   a work station for applying cords provided with devices for        applying at least one first layer of textile or metal cords,        arranged circumferentially on the radially outer belt layer;    -   at least one tread band building work station provided with        devices for applying at least one tread band in a position        radially external to the cord layer.

Preferably, the crown structure building line comprises a work stationfor laying intermediate elements provided with devices for laying atleast one intermediate element on the first belt layer.

Such devices advantageously comprise a dispenser of a continuouselongated element of elastomeric material and actuators for moving saidfirst building drum so as to wind said continuous elongated elementaccording to side by side or at least partially overlapped coils in aposition radially external to said first belt layer.

The crown structure building line may further comprise a sidewallbuilding work station provided with devices for building at least aportion of sidewalls in a position axially external to the tread band.

Such devices advantageously comprise a dispenser of a continuouselongated element of elastomeric material and actuators for moving atleast one between said first or second building drum so as to wind saidcontinuous elongated element according to side by side or at leastpartially overlapped coils.

According to one embodiment of the invention the building plantcomprising at least two tread band building work stations.

Preferably, the work station for applying a first belt of the crownstructure building line is also provided with devices for applying athird belt layer in a position radially internal to said first beltlayer.

Even more preferably, the crown structure building line comprises,upstream of said first belt application work station, a work station forapplying a third belt provided with devices for applying a third beltlayer in a position radially internal to said first belt layer.

Preferably, the work station for applying a second belt of the crownstructure building line is also provided with devices for applying athird belt layer in a position radially external to said second beltlayer.

As an alternative, the crown structure building line comprises,downstream of said second belt application work station, a work stationfor applying a third belt provided with devices for applying a thirdbelt layer in a position radially external to said second belt layer.

Preferably, a tread band sublayer application work station is positioneddownstream of the work station for applying the cords, provided withdevices for applying at least one tread band sublayer in a positionradially external to the cord layer.

Such devices comprise a dispenser of a continuous elongated element ofelastomeric material and actuators for moving one between said first orsecond building drum so as to wind said continuous elongated elementaccording to side by side or at least partially overlapped coils.

According to preferred embodiments, at least one between the first beltapplication work station, the second belt application work station, thethird belt application work station and the cord application workstation is operatively associated with at least one unit for supplyingelementary semi-finished products in the respective work stations.

Preferably, said elementary semi-finished product supplying work stationsupplies strips of elastomeric material in a continuous manner or cut tosize and comprising at least one textile or metal elongated reinforcingelement thereinside.

Advantageously, the building plant also comprises a line for preparingelementary semi-finished products suitable for being supplied in atleast one between the carcass structure building line and the crownstructure building line.

According to preferred embodiments, the plant comprises devices foradjusting the dimensions of at least one between the first buildingdrum, the second building drum and the auxiliary drum.

In particular, it is preferable that the first building drum isadjustable in radial direction.

Preferably, the second building drum is adjustable in radial direction.

Preferably, the auxiliary drum is adjustable in radial direction and inaxial direction.

Advantageously, the crown structure building line is provided withdevices for transferring the building drum from a work station of thesame crown structure building line to the next work station.

Preferably, said devices for transferring the building drum from a workstation to the next work station comprise at least one robotized arm.

Advantageously, the dimensions of said transfer devices are adjustable.

In particular, the transfer devices are adjustable in radial direction.

In particular, the transfer devices are adjustable in axial direction.

Preferably, the transfer devices comprise a plurality of sectors.

Further features and advantages of the invention will appear moreclearly from the following description of some preferred examples ofbuilding plants and processes according to the invention, made by way ofan indicative non-limiting example with reference to the annexeddrawings, wherein:

FIG. 1 shows a schematic layout of a plant for building tyres forvehicle wheels wherein the process according to one embodiment of thepresent invention is carried out;

FIG. 2 shows a detail of FIG. 1 which shows in detail a belt turning upwork station according to one embodiment of the invention;

FIGS. 3 a-3 m show the turning up work station of FIG. 2 during thedifferent operating steps of the building process according to oneembodiment of the present invention.

With reference to FIG. 1, reference numeral 1 globally indicates a plantfor building tyres for vehicle wheels according to the presentinvention.

The building plant 1 comprising a carcass structure building line 2 anda crown structure building line 3.

The carcass structure of the tyre to be built comprises at least onecarcass ply and a pair of annular anchoring structures while the crownstructure comprises at least one belt structure and a tread band.

The crown structure building line 3 comprises at least one firstbuilding drum 7 whereon an annular assembly 4 comprising a first beltlayer and at least one second belt layer radially external to said firstbelt layer is built.

The crown structure building line 3 further comprises at least oneauxiliary drum 8 whereon axially opposite end portions of said firstbelt layer are turned up so as to obtain at least a partial overlappingof the end portions of the first belt layer on said at least one secondbelt layer.

The crown structure building line 3 also includes a second building drum7′ suitable for receiving the annular assembly 4 with the axiallyopposite end portions of said first belt layer turned up on said atleast one second belt layer.

In other words, the assembly is built on a first building drum 7, andafter the turning up operation it is transferred on a second buildingdrum 7′, preferably geometrically different from the first building drum7.

In particular, said second building drum 7′ comprises a shaping surface,preferably convex, as shown in FIGS. 3 i-3 m.

With special reference now to FIG. 2, it is shown that the crownstructure building line 3 further comprises at least one transfer device9 of said annular assembly 4 from said at least one first building drum7 to said at least one auxiliary drum 8 and from the latter to said atleast one second building drum 7′.

In one alternative embodiment, not shown in the figures, the auxiliarydrum 8 is geometrically different from the first building drum 7.

In fact, it may comprise a shaping surface, preferably convex, ifnecessary.

As shown in FIG. 1, the crown structure building line 3 comprises aturning up work station 28 which in turn includes the auxiliary drum 8and the transfer device 9.

Such turning up work station 28 further comprises devices for turning upat least a part of the axially opposite end portions of the first beltlayer on said at least one second belt layer. Such turning devices, notshown in the figures, are suitable for cooperating with said auxiliarydrum 8 in carrying out the turning up operation.

The crown structure building line 3 also comprises a work station forapplying the under-belt layer 20 provided with devices for applying anunder-belt layer on the first building drum 7.

Such under-belt layer application work station 20 is arranged upstreamof the subsequent work stations of the crown structure building line 3.

The devices for applying an under-belt layer comprise a dispenser of acontinuous elongated element of elastomeric material and actuators formoving the first building drum 7 so as to wind said continuous elongatedelement according to side by side or at least partially overlapped coilsin a position radially external to the said building drum 7.

The following work stations of the crown structure building line 3 arefurther arranged upstream of the turning up work station 28:

-   -   a work station for applying a first belt 21 provided with        devices for applying at least one first belt layer in a position        radially external to the first building drum 7; and    -   a work station for applying a second belt 23 provided with        devices for applying a second belt layer in a position radially        external to the first belt strip.

Moreover, the crown structure building line 3 comprises the followingwork stations downstream of the turning up work station 28:

-   -   a cord application work station 24 provided with devices for        applying at least one first layer of textile or metal cords,        arranged circumferentially on the radially outer belt layer,        these being preferably applied at least at the axially outer        portions thereof; and    -   at least one tread band building work station 25 provided with        devices for applying at least one tread band in a position        radially external to said cord layer.

The crown structure building line 3 further comprises a work station 22for laying intermediate elements provided with devices for laying atleast one intermediate element on the first belt layer.

This work station 22 is arranged upstream of the second belt applicationwork station 23 and the relevant devices comprise a dispenser of acontinuous elongated element of elastomeric material and actuators formoving said first building drum 7 so as to wind said continuouselongated element according to side by side or at least partiallyoverlapped coils in a position radially external to said first beltlayer.

According to the embodiment shown in FIG. 1, the crown structurebuilding line 3 further comprises a sidewall building work station 26provided with devices for building at least a portion of sidewalls in aposition axially external to the tread band.

Preferably, such devices comprise a dispenser of a continuous elongatedelement of elastomeric material and actuators for moving one betweensaid first or second building drum 7, 7′ so as to wind said continuouselongated element according to side by side or at least partiallyoverlapped coils.

The continuous elongated element is supplied by a supplying line, notshown in the figures, which supplies a semi-finished product shaped as acontinuous strip of elastomeric material, wherefrom crops ofpredetermined length, correlated to the desired specification of thetyre to be obtained, are optionally cut.

The building plant 1 shown in FIG. 1 comprises two tread band buildingwork stations 25, but it may also comprise a greater number thereof, ifrequired by specific requirements of the final product.

In each of said tread band building work stations 25, said applicationdevices comprise a dispenser of a continuous elongated element ofelastomeric material and actuators for moving one of said first orsecond building drum 7, 7′ so as to wind said continuous elongatedelement according to side by side or at least partially overlapped coilsin a position radially external to said belt structure.

The work station for applying the first belt 21 may also be providedwith devices for applying a third belt layer in a position radiallyinternal to said first belt layer.

As an alternative, the crown structure building line 3 comprises,upstream of the first belt application work station 23, a work stationfor applying a third belt 27 (not shown in FIG. 1) provided with devicesfor applying a third belt layer in a position radially internal to saidfirst belt layer.

The work station for applying the second belt 23 may also be providedwith devices for applying a third belt layer in a position radiallyexternal to said second belt layer.

As an alternative, the crown structure building line 3 comprises,downstream of the second belt application work station 23, a workstation for applying a third belt 27 (not shown in FIG. 1) provided withdevices for applying a third belt layer in a position radially externalto said second belt layer.

Preferably, said third belt layer is axially less extended than saidfirst belt layer and second belt layer.

According to one embodiment not shown in the figures, a tread bandsublayer application work station is arranged downstream of the cordapplication work station 24, provided with devices for applying at leastone tread band sublayer in a position radially external to said beltstructure and preferably to said cord layer.

Also such devices comprise a dispenser of a continuous elongated elementof elastomeric material and actuators for moving one between said firstor second building drum 7, 7′ so as to wind said continuous elongatedelement according to side by side or at least partially overlappedcoils.

At least one between the first belt application work station 21, thesecond belt application work station 23, the third belt application workstation 27, and the cord application work station 24 is operativelyassociated with at least one unit for supplying elementary semi-finishedproducts 37 in the respective work stations.

However, it is preferable that one elementary semi-finished productsupplying unit 37 is associated with each of them.

Semi-finished products in the shape of continuous strip are advanced ina known manner along each unit for supplying elementary semi-finishedproducts 37, which are then optionally cut into crops of lengthcorresponding to the desired specification or of the annular assembly 4whereon they are supplied.

Each of said elementary semi-finished product supplying work stationstherefore supplies strips of elastomeric material in a continuous manneror cut to size and comprising at least one textile or metal elongatedreinforcing element thereinside.

The building plant 1 shown in FIG. 1 further comprises a line forpreparing elementary semi-finished products 31 suitable for beingsupplied in at least one between the carcass structure building line 2and the crown structure building line 3.

The building plant 1 may be provided with devices for adjusting thedimensions of at least one between the first building drum 7, the secondbuilding drum 7′ and the auxiliary drum 8.

It is preferable that the first building drum 7 and/or the secondbuilding drum 7′ is adjustable in radial direction and that theauxiliary drum 8 is adjustable both in radial direction and in axialdirection.

The crown structure building line 3 is provided with devices fortransferring the building drum 7, 7′ from a work station of the samecrown structure building line 3 to the next work station. As shown inFIGS. 1 and 2, said devices for transferring the building drum 7, 7 froma work station to the next work station comprise at least one robotizedarm 38.

The dimensions of the transfer devices 9 are adjustable and, preferably,in radial and/or axial direction.

These transfer devices 9 comprise a plurality of sectors, not shown inthe figures. Always with reference to FIG. 1, it is visible that in oneembodiment the crown structure building line 3 comprises:

-   -   an annular assembly building unit 34 wherein the annular        assembly 4 is built, comprising a first belt layer and at least        one second belt layer radially external to said first belt        layer, on said at least one first building drum 7, preferably        comprising an under-belt layer application work station 20 and        at least one first belt application work station 21, and one        second belt application work station 23;    -   a turning up work station 28 wherein the axially opposite end        portions of the first belt layer are turned up on said at least        one second belt layer; and    -   a crown structure completing unit 35 wherein the crown structure        is completed on a second building drum 7′, preferably comprising        a cord application work station 24, at least one tread band        building work station 25 and preferably a sidewall building work        station 26.

In other words, the annular assembly building unit 34 is suitable forcarrying out the pre-turning up operations on the first building drum 7and the crown structure completing unit 35 is suitable for carrying outthe post-turning up operations on the second building drum 7′.

With reference to the building plant 1 illustrated in FIG. 1, apreferred embodiment of a process for building tyres for vehicle wheelsshall now be described.

According respectively to a step i) and to a step ii), a process forbuilding tyres for vehicle wheels provides the building of a carcassstructure of a green tyre in at least one carcass structure buildingline 2, and the building of a crown structure of a green tyre in atleast one crown structure building line 3.

The carcass structure comprises at least one carcass ply and a pair ofannular anchoring structures and the crown structure comprises a beltstructure and a tread band.

Such step ii) of building the crown structure comprises at least onestep iii) of building the belt structure which, according to the presentinvention, comprises the steps a)-d) described below.

According to a step a), an annular assembly 4 comprising a first beltlayer and at least one second belt layer radially external to said firstbelt layer, is built on at least one first building drum 7.

Afterwards, the annular assembly 4 is transferred on at least oneauxiliary drum 8, according to a step b) of the present invention, shownin FIG. 3 e.

Afterwards, a step c) of turning up axially opposite end portions of thefirst belt layer is carried out so as to obtain at least a partialoverlapping of the end portions of the first belt layer on said at leastone second radially outer belt layer.

Preferably, such step c) of turning up is carried out in a turning upwork station 28 of the crown structure building line 3, shown in FIG. 1.

In that case, also step b) of transferring the annular assembly 4 on atleast one auxiliary drum 8 is carried out in said turning up workstation 28.

Finally, the step d) of transferring said annular assembly 4 from saidat least one auxiliary drum 8 on at least one second building drum 7′ iscarried out, as shown in FIGS. 3 f-3 m.

Also such step d) of transferring said annular assembly 4 from said atleast one auxiliary drum 8 on said at least one second building drum 7′is optionally carried out in said turning up work station 28.

According to one embodiment of the invention not shown in the figures,the step a) of building the annular assembly 4 comprises the furtherstep of building a third belt layer radially internal to said first beltlayer.

In this case, the step c) of turning up comprises the step of turning upaxially opposite end portions of said first intermediate belt layerbetween said third belt layer and said second belt layer so as to obtainat least a partial overlapping of the end portions of the first beltlayer on said second belt layer radially external to the first beltlayer.

According to a further embodiment of the invention not shown in thefigures, the step a) of building the annular assembly 4 comprises thefurther step of building a third belt layer radially external to saidsecond belt layer.

In this case, the step c) of turning up comprises the step of turning upaxially opposite end portions of said first radially inner belt layer soas to obtain at least a partial overlapping of the end portions of thefirst belt layer on said second belt layer radially external to thefirst belt layer and on said third belt layer radially external to saidsecond belt layer.

In any case, the end portions of the radially outermost end portions ofthe annular assembly 4 are turned up on at least one radially innermostlayer.

According to one embodiment not shown in the figures, the secondbuilding drum 7′ coincides with the first building drum 7. That is, oncefinished the turning up operation, the annular assembly 4 is transferredagain on the first building drum 7 whereon the subsequent building stepswill take place into the crown structure completing unit 35.

According to one preferred embodiment, the step iii) of building thecrown structure comprises, before step a) of building the annularassembly 4, the step a1) of applying an under-belt layer in a positionradially external to the first building drum 7.

Preferably, said step a) of building the annular assembly 4 comprisesthe sub-step a2) of laying at least one intermediate element on thefirst belt layer.

The step a1) and/or the sub-step a2) are carried out by applying atleast one continuous elongated element of elastomeric material accordingto side by side or partially overlapped coils in a position radiallyexternal respectively to said first building drum 7 and/or to said firstbelt layer.

After step d), a step e) of applying at least one first layer of textileor metal cords, arranged circumferentially, in a position radiallyexternal to said annular assembly 4, is preferably carried out.

After said step e) of applying at least one cord layer, a step f) ofapplying at least one tread band in a position radially external to saidcord layer is carried out. Preferably, such tread band comprises atleast two layers of tread band.

Afterwards, at least a portion of sidewalls of the tyre being processedis preferably applied in a position axially external to said tread band,according to a step g) of the present invention.

According to preferred embodiments, before step f) of applying the treadband, a sub-step f′) of applying at least one tread band sublayer on thecord layer applied in step e) is carried out.

The above step f) and/or sub-step f′) are carried out by applying atleast one continuous elongated element of elastomeric material accordingto side by side or partially overlapped coils in a position radiallyexternal to said belt structure.

According to one preferred embodiment, at least one between steps a) ande) comprises the pre-step h) of supplying elementary semi-finishedproducts in the respective work stations.

The semi-finished products are for example dispensed in the shape of acontinuous strip, then they are optionally cut into crops of lengthcorresponding to the desired specification or of the annular assembly 4whereon they are dispensed.

Such elementary semi-finished products may therefore comprise strips ofelastomeric material optionally cut to size and comprising at least onetextile or metal elongated reinforcing element thereinside.

Said elementary semi-finished products may further be applied next toone another so that the longitudinal axis thereof exhibits at leastalong a portion the same predetermined angle with the circumferentialdirection of the first building drum 7.

The tyre building process according to this embodiment may comprises theadditional step h′) of preparing elementary semi-finished products in asemi-finished product preparation line 31.

The building process further comprises the step j) of adjusting thedimensions of at least one between the first building drum 7, the secondbuilding drum 7′ and the auxiliary drum 8.

Preferably, the step i) comprises the radial adjustment of the firstbuilding drum 7 and/or the radial adjustment of the second building drum7′ and/or the radial and axial adjustment of the auxiliary drum 8.

As visible in FIGS. 1 and 2, the first and/or the second building drum7, 7′ is transferred from a work station of the crown structure buildingline 3 to the next work station by at least one robotized arm 38.

Both for the first building drum 7 and for the second building drum 7′,are preferably provided return paths (not shown in the figures) to thefirst work station respectively into the annular assembly building unit34 and into the crown structure completing unit 35.

If the second building drum 7′ coincides with the first building drum 7,said return path carries the first building drum 7 from the last workstation of the crown structure completing unit 35 to the first workstation of the annular assembly building unit 34.

On the other hand, the step b) of transferring the annular assembly 4 onat least one auxiliary drum 8 is carried out by transfer devices 9, aswell visible in FIGS. 3 a-3 e.

Also the step d) of transferring said annular assembly 4 from said atleast one auxiliary drum 8 on said at least one first or second buildingdrum 7, 7′ is carried out by transfer devices 9. This is clearly visiblein FIGS. 3 f-3 m.

With particular reference to FIGS. 3 a-3 m, the tyre building process insteady operating conditions according to one preferred embodiment of theinvention shall now be described.

FIG. 3 a shows an annular assembly 4 built on a first building drum 7,according to the above step a).

In FIG. 3 b it is shown how the transfer devices 9 are radially adjustedup to contact the annular assembly 4.

The subsequent removal of the first building drum 7 shown in FIG. 3 c,starts the step b) of transferring the annular assembly 4 on theauxiliary drum 8. In fact, during this step, the annular assembly 4 isseparated from the building drum 7 and retained by the transfer devices9, to be then transferred to the auxiliary drum 8 during the sequentialsteps shown in FIGS. 3 d and 3 e.

FIG. 3 d shows how the transfer devices 9, wherewith the annularassembly 4 is associated, shift in the direction indicated by the arrowto position at the auxiliary drum 2 0 8. In this position, the annularassembly contacts such auxiliary drum 8 and is separated from thetransfer devices by shifting of the same towards the starting positionthereof (FIG. 3 e).

At this point, the step b) of transferring the annular assembly 4 on theauxiliary drum 8 is completed.

Subsequently the step f) of turning up, schematically shown in FIG. 3 f,is carried out.

In FIG. 3 g, the step d) of transferring the annular assembly 4 on asecond building drum 7′ starts. In such figure, in fact, it is shown howthe transfer devices 9 shift at the auxiliary drum 8 and are radiallyadjusted until they contact the annular assembly 4 with the ends turnedup.

FIG. 3 h shows how the transfer devices 9 pick up the annular assembly 4from the auxiliary drum 8 and shift towards the initial positionthereof.

In FIG. 3 i, a second building drum 7′, geometrically different from thefirst building drum 7, is arranged at the transfer devices 9.

In FIG. 3 l, the transfer devices 9 wherewith the annular assembly 4 isassociated, are radially adjusted up to contact the second building drum7′.

In FIG. 3 m, the transfer devices 9 radially move away from the secondauxiliary drum 7′ unloading the annular assembly 4 thereon and thuscompleting step d).

As mentioned before, and as partially shown in the above FIGS. 3 a-3 m,the tyre building process comprises at least one step k) of adjustingthe dimensions of said transfer devices 9. In particular, such step k)comprises the radial and/or axial adjustment of said transfer devices 9.

At least one between step b) of transferring the annular assembly 4 onat least one auxiliary drum 8 and step d) of transferring the annularassembly 4 on said at least a first or second building drum 7, 7′ isfollowed by a step l) of shaping of the belt structure.

In particular, such step is carried out by expanding respectively theauxiliary drum 8 or of the first or second building drum 7, 7′.

1-72. (canceled)
 73. A process for building a tyre for a vehicle wheelcomprising the steps of: i) building a carcass structure of a green tyrein at least one carcass structure building line, said carcass structurecomprising at least one carcass ply and a pair of annular anchoringstructures; and ii) building a crown structure of a green tyre in atleast one crown structure building line, said crown structure comprisinga belt structure and a tread band, wherein step ii) of building thecrown structure comprises at least one step iii) of building the beltstructure which comprises the steps of: a) building on at least onefirst building drum, an annular assembly comprising a first radiallyinner belt layer and at least one second belt layer radially external tosaid first belt layer; b) transferring said annular assembly on at leastone auxiliary drum; c) turning up axially opposite end portions of thefirst radially inner belt layer so as to obtain at least a partialoverlapping of the end portions of the first belt layer on said at leastone second radially outer belt layer; and d) transferring said annularassembly from said at least one auxiliary drum on at least one secondbuilding drum.
 74. The process for building a tyre according to claim73, wherein step a) of building the annular assembly, further comprisesbuilding a third belt layer.
 75. The process for building a tyreaccording to claim 74, wherein said third belt layer is radiallyexternal to said second belt layer.
 76. The process for building a tyreaccording to claim 74, wherein said third belt layer is radiallyinternal to said first belt layer.
 77. The process for building a tyreaccording to claim 75, wherein step c) of turning up axially oppositeend portions, comprises the step of turning up axially opposite endportions of said first radially inner belt layer so as to obtain atleast a partial overlapping of the end portions of the first belt layeron said second belt layer radially external to the first belt layer andon said third belt layer radially external to said second belt layer.78. The process for building a tyre according to claim 73, wherein stepiii) of building the belt structure comprises, before step a) ofbuilding the annular assembly, the step of: a1) applying an under-beltlayer in a position radially external to the first building drum. 79.The process for building a tyre according to claim 78, wherein step a)of building the annular assembly comprises the sub-step of: a2) layingat least one intermediate element on the first belt layer.
 80. Theprocess for building a tyre according to claim 73, wherein step iii)comprises, after step d): e) applying at least one first layer oftextile or metal cords, arranged circumferentially, in a positionradially external to said annular assembly.
 81. The process for buildinga tyre according to claim 80, wherein step ii) of building the beltstructure comprises, after step e) of applying at least one cord layer:f) applying at least one tread band in a position radially external tosaid cord layer.
 82. The process for building a tyre according to claim81, wherein step ii) of building the belt structure comprises, afterstep f) of applying the tread band: g) applying at least a portion ofsidewalls of the tyre being processed in a position axially external tosaid tread band.
 83. The process for building a tyre according to claim73, wherein step c) of turning up the axially opposite end portions ofsaid first radially inner belt layer on said at least one secondradially outer belt layer, is carried out in a turning up work stationof the crown structure building line.
 84. The process for building atyre according to claim 73, wherein step b) of transferring said annularassembly on at least one auxiliary drum, is carried out in a turning upwork station.
 85. The process for building a tyre according claim 73,wherein step d) of transferring said annular assembly from said at leastone auxiliary drum on said at least one second building drum is carriedout in a turning up work station.
 86. The process for building a tyreaccording to claim 81, wherein step ii) of building the belt structurecomprises, before step f) of applying the tread band: f′) applying atleast one tread band sublayer on the cord layer applied in step e). 87.The process for building a tyre according to claim 81, wherein said stepf) comprises applying two tread band layers.
 88. The process forbuilding a tyre according to claim 86, wherein at least one between stepf) and sub-step f′) is carried out by applying at least one continuouselongated element of elastomeric material according to side by side orpartially overlapped coils in a position radially external to said beltstructure.
 89. The process for building a tyre according to claim 79,wherein at least one between step a1) and step a2) is carried out byapplying at least one continuous elongated element of elastomericmaterial according to side by side or partially overlapped coils in aposition radially external to said first building drum or to said firstbelt layer.
 90. The process for building a tyre according to claim 80,wherein at least one between steps a) and e) comprises a pre-step: h)supplying elementary semi-finished products in respective work stations.91. The process for building a tyre according to claim 90, wherein saidelementary semifinished products are strips of elastomeric material cutto size and comprising at least one textile or metal elongatedreinforcing element thereinside.
 92. The process for building a tyreaccording to claim 90, wherein said elementary semi-finished productsare applied next to one another so that a longitudinal axis thereofexhibits, at least along a portion thereof, a same predetermined anglewith the circumferential direction of the first building drum.
 93. Theprocess for building a tyre according to claim 90, comprising: h′)preparing elementary semi-finished products in a semi-finished productpreparation line.
 94. The process for building a tyre according to claim73, further comprising: j) adjusting the dimensions of at least onebetween the first building drum, the second building drum and theauxiliary drum.
 95. The process for building a tyre according to claim94, wherein step j) comprises radial adjustment of the first buildingdrum.
 96. The process for building a tyre according to claim 94, whereinstep j) comprises radial adjustment of the second building drum.
 97. Theprocess for building a tyre according to claim 94, wherein step j)comprises radial and axial adjustment of the auxiliary drum.
 98. Theprocess for building a tyre according to claim 73, wherein at least onebetween said first and second building drum is transferred from a workstation of the crown structure building line to a next work station byat least one robotized arm.
 99. The process for building a tyreaccording to claim 73, wherein step b) of transferring said annularassembly on at least one auxiliary drum is carried out by transferdevices.
 100. The process for building a tyre according to claim 73,wherein step d) of transferring said annular assembly from said at leastone auxiliary drum on said at least one first or second building drum iscarried out by transfer devices.
 101. The process for building a tyreaccording to claim 99, further comprising: k) adjusting the dimensionsof said transfer devices.
 102. The process for building a tyre accordingto claim 101, wherein step k) comprises radial adjustment of saidtransfer devices.
 103. The process for building a tyre according toclaim 101, wherein said step k) comprises axial adjustment of saidtransfer devices.
 104. The process for building a tyre according toclaim 73, wherein at least one between step b) of transferring theannular assembly on at least one auxiliary drum and step d) oftransferring the annular assembly on said at least one first or secondbuilding drum is followed by: l) shaping the belt structure.
 105. Theprocess for building a tyre according to claim 104, wherein step l) ofshaping the belt structure, is carried out by expanding of the auxiliarydrum.
 106. The process for building a tyre according to claim 104,wherein step l) of shaping the belt structure, is carried out byexpanding of at least one between said first building drum and secondbuilding drum.
 107. A plant for building a tyre for a vehicle wheelcomprising: at least one carcass structure building line, said carcassstructure comprising at least one carcass ply and a pair of annularanchoring structures; and at least one crown structure building line,said crown structure comprising at least one belt structure and a treadband, wherein the crown structure building line comprises: at least onefirst building drum whereon an annular assembly comprising a firstradially inner belt layer and at least one second belt layer radiallyexternal to said first belt layer is built; at least one auxiliary drumwhereon axially opposite end portions of said first belt layer areturned up so as to obtain at least a partial overlapping of the endportions of the first belt layer on said at least one second belt layer;at least one second building drum suitable for receiving the annularassembly with the axially opposite end portions of said first belt layerturned up on said at least one second belt layer; and at least onedevice for transferring said annular assembly from said at least onefirst building drum to said at least one auxiliary drum and from said atleast one auxiliary drum to said at least one second building drum. 108.The plant for building a tyre according to claim 107, wherein said atleast one second building drum is identical to said at least one firstbuilding drum.
 109. The plant for building a tyre according to claim107, wherein said second building drum is geometrically different fromthe first building drum.
 110. The plant for building a tyre according toclaim 109, wherein said second building drum comprises a shapingsurface.
 111. The plant for building a tyre according to claim 107,wherein said auxiliary drum is geometrically different from the firstbuilding drum.
 112. The plant for building a tyre according to claim111, wherein said auxiliary drum comprises a shaping surface.
 113. Theplant for building a tyre according to claim 110, wherein said shapingsurface comprises a convex surface.
 114. The plant for building a tyreaccording to claim 107, wherein the crown structure building linecomprises at least one turning up work station comprising said at leastone auxiliary drum and said at least one transfer device.
 115. The plantfor building a tyre according to claim 114, wherein said turning up workstation further comprises devices for turning up at least a part of theaxially opposite end portions of the first belt layer on said at leastone second belt layer, suitable for cooperating with said auxiliarydrum.
 116. The plant for building a tyre according to claim 107, whereinthe crown structure building line comprises: an under-belt layerapplication work station provided with devices for applying anunder-belt layer on the first building drum.
 117. The plant for buildinga tyre according to claim 116, wherein said devices for applying anunder-belt layer, comprise a dispenser of a continuous elongated elementof elastomeric material and actuators for moving said first buildingdrum so as to wind said continuous elongated element according to sideby side or at least partially overlapped coils in a position radiallyexternal to said first building drum.
 118. The plant for building a tyreaccording to claim 114, wherein the crown structure building linecomprises, upstream of the turning up work station: a work station forapplying a first belt provided with devices for applying at least onefirst belt layer in a position radially external to said first buildingdrum; and a work station for applying a second belt provided withdevices for applying a second belt layer in a position radially externalto said first belt strip.
 119. The plant for building a tyre accordingto claim 114, wherein the crown structure building line comprises,downstream of the turning up work station: a work station for applyingcords provided with devices for applying at least one first layer oftextile or metal cords, arranged circumferentially on the radially outerbelt layer; and at least one tread band building work station providedwith devices for applying at least one tread band in a position radiallyexternal to said cord layer.
 120. The plant for building a tyreaccording to claim 107, wherein the crown structure building linecomprises a work station for laying intermediate elements provided withdevices for laying one intermediate element on the first belt layer.121. The plant for building a tyre according to claim 120, wherein saiddevices comprise a dispenser of a continuous elongated element ofelastomeric material and actuators for moving said first building drumso as to wind said continuous elongated element according to side byside or at least partially overlapped coils in a position radiallyexternal to said first belt layer.
 122. The plant for building a tyreaccording to claim 107, wherein the crown structure building linecomprises a sidewall building work station provided with devices forbuilding at least a portion of sidewalls in a position axially externalto the tread band.
 123. The plant for building a tyre according to claim122, wherein said devices comprise a dispenser of a continuous elongatedelement of elastomeric material and actuators for moving one betweensaid first or second building drum so as to wind said continuouselongated element according to side by side or at least partiallyoverlapped coils.
 124. The plant for building a tyre according to claim119, comprising at last two tread band building work stations.
 125. Theplant for building a tyre according to claim 124, wherein, in each treadband building work station, said application devices comprise adispenser of a continuous elongated element of elastomeric material andactuators for moving one of said first or second building drum so as towind said continuous elongated element according to side by side or atleast partially overlapped coils in a position radially external to saidbelt structure.
 126. The plant for building a tyre according to claim118, wherein said work station for applying the first belt of the crownstructure building line is also provided with devices for applying athird belt layer in a position radially internal to said first beltlayer.
 127. The plant for building a tyre according to claim 118,wherein the crown structure building line comprises, upstream of saidfirst belt application work station, a work station for applying a thirdbelt provided with devices for applying a third belt layer in a positionradially internal to said first belt layer.
 128. The plant for buildinga tyre according to claim 118, wherein said work station for applyingthe second belt of the line for building the crown structure is alsoprovided with devices for applying a third belt layer in a positionradially external to said second belt layer.
 129. The plant for buildinga tyre according to claim 118, wherein the crown structure building linecomprises, downstream of said second belt application work station, awork station for applying a third belt provided with devices forapplying a third belt layer in a position radially external to saidsecond belt layer.
 130. The plant for building a tyre according to claim119, wherein the crown structure building line comprises, downstream ofthe cord application work station, a tread band sublayer applicationwork station provided with devices for applying at least one tread bandsublayer in a position radially external to the cord layer.
 131. Theplant for building a tyre according to claim 130, wherein said devicesfor applying at least one tread band sublayer, comprise a dispenser of acontinuous elongated element of elastomeric material and actuators formoving one between said first or second building drum so as to wind saidcontinuous elongated element according to side by side or at leastpartially overlapped coils.
 132. The plant for building a tyre accordingto claim 119, wherein at least one between the first belt applicationwork station, the second belt application work station, the third beltapplication work station, and the cord application work station isoperatively associated with at least one unit for supplying elementarysemi-finished products in the respective work stations.
 133. The plantfor building a tyre according to claim 132, wherein said work stationfor supplying elementary semi-finished products dispenses strips ofelastomeric material in a continuous manner or cut to size, comprisingat least one textile or metal elongated reinforcing element thereinside.134. The plant for building a tyre according to claim 107, comprising aline for preparing elementary semi-finished products capable of beingsupplied in at least one between the carcass structure building line andthe crown structure building line.
 135. The plant for building tyresaccording to claim 107, comprising devices for adjusting the dimensionsof at least one between the first building drum, the second buildingdrum and the auxiliary drum.
 136. The plant for building a tyreaccording to claim 107, wherein the first building drum is adjustable ina radial direction.
 137. The plant for building a tyre according toclaim 107, wherein the second building drum is adjustable in a radialdirection.
 138. The plant for building a tyre according to claim 107,wherein the auxiliary drum is adjustable in a radial direction and in anaxial direction.
 139. The plant for building a tyre according to claim107, wherein the crown structure building line is provided with devicesfor transferring the building drum from a work station of the same crownstructure building line to the next work station.
 140. The plant forbuilding a tyre according to claim 139, wherein said transfer devices ofthe first building drum from a work station to the next work stationcomprise at least one robotized arm.
 141. The plant for building a tyreaccording to claim 107, wherein dimensions of said transfer devices areadjustable.
 142. The plant for building a tyre according to claim 141,wherein said transfer devices are adjustable in a radial direction. 143.The plant for building a tyre according to claim 141, wherein saidtransfer devices are adjustable in an axial direction.
 144. The plantfor building a tyre according to claim 141, wherein said transferdevices comprise a plurality of sectors.